The number 278,460 can be evenly divided by 1 2 3 4 5 6 7 9 10 12 13 14 15 17 18 20 21 26 28 30 34 35 36 39 42 45 51 52 60 63 65 68 70 78 84 85 90 91 102 105 117 119 126 130 140 153 156 170 180 182 195 204 210 221 234 238 252 255 260 273 306 315 340 357 364 390 420 442 455 468 476 510 546 585 595 612 630 663 714 765 780 819 884 910 1,020 1,071 1,092 1,105 1,170 1,190 1,260 1,326 1,365 1,428 1,530 1,547 1,638 1,785 1,820 1,989 2,142 2,210 2,340 2,380 2,652 2,730 3,060 3,094 3,276 3,315 3,570 3,978 4,095 4,284 4,420 4,641 5,355 5,460 6,188 6,630 7,140 7,735 7,956 8,190 9,282 9,945 10,710 13,260 13,923 15,470 16,380 18,564 19,890 21,420 23,205 27,846 30,940 39,780 46,410 55,692 69,615 92,820 139,230 and 278,460, with no remainder.
Since 278,460 cannot be divided by just 1 and 278,460, it is a composite number.